Place it at the reveal when the hidden person steps into frame, then cut straight to a Bruh reaction for the payoff. If the moment needs a bigger finish, follow it with a Scream Meme instead, keeping the behind-you moment as the centre of the edit.
About this sound
This is a 14-second Portuguese voice clip built around Xandão asking who is standing behind him. The line is delivered as a direct, suspicious question, turning a simple check over the shoulder into a comic moment. It feels playful and wary at once, with the humour coming from the sudden sense that someone is right there. It works best as a quick reaction to being followed or surprised.